--- a/engine.c	Sun Sep 09 20:52:54 2007 +0000
+++ b/engine.c	Sun Sep 09 22:35:21 2007 +0000
@@ -372,7 +372,7 @@
 {
 	StringID str;
 
-	if (!IsEngineIndex(p1) || _cmd_text[0] == '\0') return CMD_ERROR;
+	if (!IsEngineIndex(p1) || _cmd_text == NULL || _cmd_text[0] == '\0') return CMD_ERROR;
 
 	str = AllocateNameUnique(_cmd_text, 0);
 	if (str == 0) return CMD_ERROR;

--- a/misc_cmd.c	Sun Sep 09 20:52:54 2007 +0000
+++ b/misc_cmd.c	Sun Sep 09 22:35:21 2007 +0000
@@ -187,7 +187,7 @@
 	StringID str;
 	Player *p;
 
-	if (_cmd_text[0] == '\0') return CMD_ERROR;
+	if (_cmd_text == NULL || _cmd_text[0] == '\0') return CMD_ERROR;
 
 	str = AllocateNameUnique(_cmd_text, 4);
 	if (str == 0) return CMD_ERROR;

--- a/signs.c	Sun Sep 09 20:52:54 2007 +0000
+++ b/signs.c	Sun Sep 09 22:35:21 2007 +0000
@@ -151,7 +151,7 @@
 
 	/* If _cmd_text 0 means the new text for the sign is non-empty.
 	 * So rename the sign. If it is empty, it has no name, so delete it */
-	if (_cmd_text[0] != '\0') {
+	if (_cmd_text != NULL && _cmd_text[0] != '\0') {
 		/* Create the name */
 		StringID str = AllocateName(_cmd_text, 0);
 		if (str == 0) return CMD_ERROR;

--- a/station_cmd.c	Sun Sep 09 20:52:54 2007 +0000
+++ b/station_cmd.c	Sun Sep 09 22:35:21 2007 +0000
@@ -2645,7 +2645,7 @@
 	StringID str;
 	Station *st;
 
-	if (!IsValidStationID(p1) || _cmd_text[0] == '\0') return CMD_ERROR;
+	if (!IsValidStationID(p1) || _cmd_text == NULL || _cmd_text[0] == '\0') return CMD_ERROR;
 	st = GetStation(p1);
 
 	if (!CheckOwnership(st->owner)) return CMD_ERROR;

--- a/town_cmd.c	Sun Sep 09 20:52:54 2007 +0000
+++ b/town_cmd.c	Sun Sep 09 22:35:21 2007 +0000
@@ -1373,7 +1373,7 @@
 	StringID str;
 	Town *t;
 
-	if (!IsValidTownID(p1) || _cmd_text[0] == '\0') return CMD_ERROR;
+	if (!IsValidTownID(p1) || _cmd_text == NULL || _cmd_text[0] == '\0') return CMD_ERROR;
 
 	t = GetTown(p1);
 

--- a/vehicle.c	Sun Sep 09 20:52:54 2007 +0000
+++ b/vehicle.c	Sun Sep 09 22:35:21 2007 +0000
@@ -2633,7 +2633,7 @@
 	Vehicle *v;
 	StringID str;
 
-	if (!IsValidVehicleID(p1) || _cmd_text[0] == '\0') return CMD_ERROR;
+	if (!IsValidVehicleID(p1) || _cmd_text == NULL || _cmd_text[0] == '\0') return CMD_ERROR;
 
 	v = GetVehicle(p1);
 

--- a/waypoint.c	Sun Sep 09 20:52:54 2007 +0000
+++ b/waypoint.c	Sun Sep 09 22:35:21 2007 +0000
@@ -319,7 +319,7 @@
 	wp = GetWaypoint(p1);
 	if (!CheckTileOwnership(wp->xy)) return CMD_ERROR;
 
-	if (_cmd_text[0] != '\0') {
+	if (_cmd_text != NULL && _cmd_text[0] != '\0') {
 		StringID str = AllocateNameUnique(_cmd_text, 0);
 
 		if (str == 0) return CMD_ERROR;